The present invention relates to an improved caulking tube and more particularly relates to a caulking tube having an improved seal to the passage of air and moisture at the point where the plunger member comes in contact with the rear end of the caulking tube body.
Caulking tubes are well known. There are many designs on the market. Generally, such a caulking tube comprises a tubular body member, a plate attached at one end with an opening therein to which is affixed a protruding sealed nozzle. After the tube is filled, there is inserted at the rear end of the tubular body a plunger member to seal the tube.
To utilize the caulking tube, generally, the tube is inserted into a caulking gun and the sealed tip of the nozzle is cut open in one fashion or another. Then the ram of the caulking gun acts against the plunger forcing the material in the caulking tube out of the now opened nozzle member.
Such caulking tubes usually are utilized to package materials and more specifically sealants in an anhydrous state and to prevent them from coming in contact with the moisture in the air. Most materials that are packaged in caulking tubes upon being exposed to air or the moisture in the air will cure to a hard solid state.
Accordingly, it is highly desirable in the packaging of such materials in caulking tubes that the caulking tubes be as impervious to the passage of air as possible such that the material inside will have a long utility life.
One such sealant material which is packaged in caulking tubes and has to be maintained in an anhydrous state prior to cure is room temperature vulcanizable silicone rubber compositions. Such compositions remain uncured in the anhydrous state but when exposed to the moisture in the atmosphere cure to a solid silicone elastomer. Accordingly, it is highly desirable to package such room temperature vulcanizable silicone rubber compositions in caulking tubes such that such caulking tubes are as airtight as possible without unduly increasing the expense of the tube.
An especially difficult problem in the manufacture and packaging of such materials as room temperature vulcanizable silicone rubber compositions or other sealants in caulking tubes has been to produce an airtight seal with the plunger member. Even though the plunger member is usually a few thousandths of an inch larger than the caulking tube and is forced into the rear end of the caulking tube to make as tight a seal as possible, it has been found that nevertheless an airtight seal in most cases is not produced.
Accordingly, various methods have been tried to solve this problem. For instance, there have been utilized heat sealed aluminum and metal foil caps at the rear end of the caulking tube over the plunger. The difficulty with such metal foil caps is that they unduly increase the expense of the caulking tube and in addition are easily damaged or punctured. End plastic caps have also been tried but these have the same disadvantages as the aluminum foil cap and in addition have been found not to be airtight.
Some manufacturers have utilized adhesives or glues to be applied over the rear end of the caulking tube after the plunger is inserted to produce an airtight seal of the plunger member with the rear end of the caulking tube. The difficulty with this approach is it is a difficult method to apply in manufacturing practices of the filling of caulking tubes with sealant material. Further, difficulties have been encountered by users of the caulking tube as the result of the adherence of the plunger to the interior side of the caulking tube due to the adhesive.
A more advanced approach has been to utilize various non-adhesive coatings applied to the rear end of the plunger and the caulking tube after the plunger has been inserted into the tube. While this approach has been found to be less expensive and creates less difficulties for the user, it has been found that even in these cases airtight seals were not produced in all cases. One reason for this is that in the packaging of some materials in caulking tubes, such materials are poured into the caulking tubes at elevated temperatures and the plunger is inserted. Accordingly, when the material in the caulking tube cools, the plunger is drawn inward and is forced into the tube breaking any seal that may be formed by such exterior coatings as described above. It has been found that a coating with certain materials on the inside of the rear end of the caulking tube produces a superior airtight seal with a plunger without unduly increasing the cost of the caulking tube.
Accordingly, it is one object of the present invention to produce a caulking tube with an improved seal between the plunger member and the rear end of the caulking tube.
It is another object of the present invention to provide an economic caulking tube with an improved seal between the plunger member and the rear end of the caulking tube.
It is still another object of the present invention to provide for an improved caulking tube with a superior seal at the rear end of the tube which allowed the contents of the tube to have a shelf life of 2 years or more.
It is still an additional object of the present invention to provide a simple and economic process for producing an airtight seal between the plunger and the rear end of the caulking tube.
These and other objects of the present invention are accomplished by means of the disclosure set forth hereinbelow.